Various types of manufactured combustible elements are known, including briquettes or "sawdust logs" formed from bound, consolidated wood materials such as chips and sawdust. It is a particular characteristic of such sawdust logs or briquettes that they no longer have the burning characteristics of fragmented wood, but rather tend to burn relatively quickly and over a short duration in a hot fire, which reduces the efficiency of the stove, shortens the life and otherwise abuses both the stove and the flue.
The most relevant examples of the prior art known to applicant appear in U.S. Pat. Nos. 4,308,032; 2,222,250; 4,060,396; 3,947,255, 3,726,651 and 4,243,394.
U.S. Pat. No. 4,308,032 describes a compacted sawdust log of cylindrical configuration which is intended to be handmade by the user. There is no teaching of the provision of a combustion channel.
U.S. Pat. No. 2,222,250 describes a cylindrically laminated briquette formed of vegetable fiber, such as wood, bond by inherent resins. Here also there is no teaching of the provision of a combustion channel.
U.S. Pat. No. 4,060,396 describes a briquette formed of compacted wood particles in the form of interlocked disc-shaped wafers and having a central channel. The briquette is highly compressed and bound by natural resins and is intended for quick burning.
U.S. Pat. No. 3,947,255 describes a method of manufacturing consolidated elements based on bark and binders and having the configuration of a sector of a circle.
U.S. Pat. No. 3,726,651 also describes a consolidated burning element having a central bore. U.S. Pat. No. 4,243,394 illustrates a channeled consolidated element. FIG. 3 of this Patent illustrates a preferred packaging arrangement of such elements. U.S. Pat. Nos. 57,890 and 4,243,393 also illustrate combustion elements having a central bore.